The present invention concerns a power supply arrangement for an electronic tuning system.
A variety of electronic tuning systems for radio and television are known. A number of these include a non-volatile memory for storing information for tuning various channels. The contents of memory locations within the memory are programmed with tuning information for respective channels during a set-up procedure. When a channel is selected the appropriate memory location is addressed, and its contents are read out and used to tune the receiver to the selected channel.
Since non-volatile memories are capable of retaining information almost indefinitely without power, it is not necessary to preprogram again after a period in which the receiver has been off or disconnected from the line. A non-volatile memory often includes an integrated circuit array of metal-nitride-oxide-semiconductor (MNOS) memory cells.
The power supply voltage applied to the memory is selected to enable the memory to be programmed during set up and to be interrogated during channel selection. For MNOS non-volatile memories the magnitude of the power supply voltage required for these purposes is in the order of 30 volts. When the memory is not being programmed or interrogated, no power supply voltage is needed to maintain the information in the memory; so a considerable amount of power is wasted. In addition, the uninterrupted maintenance of a high supply voltage tends to reduce the reliability of such memories.
The present invention concerns a power supply arrangement for a tuning system including apparatus for reducing the magnitude of a supply voltage for the tuning system during dormant periods when tuning information for the selection of channels is not being changed.
In a preferred embodiment of the present invention, in a tuning system including a non-volatile memory for storing tuning information, control apparatus is provided in a power supply arrangement for normally maintaining the magnitude of the supply voltage for the memory at a relatively low level and for increasing the magnitude of the power supply voltage to a higher change-enabling level when the memory is interrogated during channel selection or when the contents of the memory are being programmed. Desirably, the low level is selected at a compromise value to provide both for relatively short switching times between dormant and active states and for relatively low power consumption during the dormant state.